sandbox: convert shim metrics errors to native errors

controllerLocal.Metrics returned the shim's gRPC status error as is,
unlike every other method of the controller. CRI's pod stats listing
tolerates NotFound and Unavailable from a controller but never matched a
status error, so one sandbox whose shim could not report metrics failed
ListPodSandboxStats for every pod on the node.

Signed-off-by: Maksym Pavlenko <pavlenko.maksym@gmail.com>

plugins/sandbox/controller.go

@@ -339,7 +339,7 @@ func (c *controllerLocal) Metrics(ctx context.Context, sandboxID string) (*types
 	req := &runtimeAPI.SandboxMetricsRequest{SandboxID: sandboxID}
 	resp, err := sb.SandboxMetrics(ctx, req)
 	if err != nil {
-		return nil, err
+		return nil, errgrpc.ToNative(err)
 	}
 	return resp.Metrics, nil
 }